Rolling mills

ABSTRACT

TO ADJUST THE ROLL GAP OF A ROLLING MILL HYDRAULIC PISTON AND CYLINDER ASSEMBLIES ACT BETWEEN THE HOUSINGS OF THE MILL AND THE ROLLS, AND ECH ASSEMBLY HAS ITS OWN POSITIONAL CONTROL SYSTEM WHICH IS ARRANGED TO MAINTAIN THE PISTON AT A DATUM POSITION RELATIVE TO ITS CYLINDER AND AN AUTOMATIC CONTROL SYSTEM SUCH AS A GAUGE METER DETECTS DEPARTURE OF THE STRIP GAUGE FROM A REQUIRED VALUE AND ADJUSTS THE DATUM POSITION OF AT LEAST ONE OF THE PISTON AND CYLINDER ASSEMBLIES TO COMPENSATE FOR THE VARIATION IN GAUGE. THE PISTON AND CYLINDER ASSEMBLIES MAY REPLACE THE CONVENTIONAL SCREWDOWN SCREWS OF THE MILL OR ALTERNATIVELY THEY MAY ACT IN SERIES WITH THE SCREWS.

March 9 1971 g BQND ETAL 3,568,484

' ROLLING MILLS Filed March 1, 1968 2 Sheets-Sheet 1 Hal March 9, 1971 QND ETAL 3,568,484

I ROLLING MILLS I Filed March 1, 1968 2 Sheets-Sheet z United States Patent Oifice 3,568,484 ROLLING MILLS Harry Laurence Fred Bond, Hathersage, near Shefiield, Dennis Stubbs, Sheffield, and Bela Istvan Bathory, Wales, near Shefiield, England, assignors to Davy and United Engineering Company Limited, Sheffield, England Filed Mar. 1, 1968, Ser. No. 709,607 Claims priority, application Great Britain, Mar. 2, 1967, 9,977/ 67 Int. Cl. 1321b 37/12 US. Cl. 72-8 4 Claims ABSTRACT OF THE DISCLOSURE To adjust the roll gap of a rolling mill hydraulic piston and cylinder assemblies act between the housings of the mill and the rolls, and each assembly has its own positional control system which is arranged to maintain the piston at a datum position relative to its cylinder and an automatic control system such as a gaugemeter detects departure of the strip gauge from a required value and adjusts the datum position of at least one of the piston and cylinder assemblies to compensate for the variation in gauge. The piston and cylinder assemblies may replace the conventional screwdown screws of the mill or alternatively they may act in series with the screws.

This invention relates to rolling mills and is particularly concerned with rolling mills for rolling to prescribed thickness metals, such as steel and aluminium.

In accordance with the present invention, a rolling mill has, for the adjustment of the gap between the work rolls, hydraulic piston and cylinder assemblies acting between the mill housings and the rolls, with each piston and cylinder assembly having its own positional control system arranged to maintain the piston at a datum position relative to its cylinder, and an automatic control system comprising means for detecting departure of the thickness of material being rolled by the mill from a required value and for adjusting the datum position of at least one of the piston and cylinder assemblies in accordance with the detected departure to reduce the departure substantially to Zero.

Each piston and cylinder assembly preferably replaces the conventional screwdown screw of the rolling mill. Alternatively, the screws may be retained, with a pair of the piston and cylinder assemblies acting in series one with each of the screws; in this latter case, coarse adjustment of roll gap may be effected by the screws and fine adjustment by the assemblies.

Preferably, the means for detecting the departure of the strip is the so-called Gaugemeter, as described in US. Pat. No. 2,726,541 entitled Measuring Apparatus for Rolling or Drawing Sheet or Strip Material that issued to R. B. Sims on Dec. 13, 1955 and elsewhere. In that case, the S signal representing the roll setting, may be derived from the positions at which the pistons of the assemblies are set.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings in which FIGS. 1 and 2 are a side and a sectional front elevation respectively of a rolling mill in which the roll gap is adjusted solely by hydraulic means,

FIG. 3 is a diagram of a control circuit suitable for controlling the mill shown in FIGS. 1 and 2,

FIG. 4 is a diagram of an alternative control circuit to that shown in FIG. 3,

FIG. 5 is an end elevation, partly in section of a roll- 3,568,484 Patented Mar. 9, 1971 ing mill having both screws and hydraulic means for controlling the roll gap, and

FIG. 6 is a diagram of a control circuit suitable for controlling the mill shown in FIG. 5.

Referring to the rolling mill shown in FIGS. 1 and 2, the mill is of conventional form with work rolls 1 and 2, and backup rolls 3 and 4, journalled in the windows of two housings 5 and 6 spaced apart in the direction of the axes of the rolls. Instead of the usual screws which are threaded into nuts in the housings and which bear against the chocks of the upper work roll or upper backup roll, each housing has a piston-and-cylinder assembly 7, with the cylinder secured in the top of the housing and the piston acting against the chock of the upper work roll or back-up roll. A transducer 8 is associated with each assembly. The assemblies are the sole means for adjusting the roll gap. It will be appreciated that the piston-and-cylinder assemblies could be equally well arranged in the bottoms of the windows and acting against the bottom chocks arranged in the windows.

Although it has been stated that the piston-and-cylinder assemblies are the sole means for adjusting the gap between the work rolls, it will be understood that owing r to the reduction in the diameter of the work and the back-up rolls due to wear of the rolls it may be necessary to insert packing pieces between the assemblies and the roll chocks to take up the change in the overall dimension between the upper and lower surfaces of the upper and lower back-up roll chocks respectively. It is intended in this specification that the term solely should include the case where packing members are fitted to the mill.

The rolling mill also has an automatic gauge control system, which detects any departure of the thickness of the strip leaving the mill from a required value and adjusts the roll gap to maintain the thickness at the required value. The automatic gauge control system illustrated in FIG. 3 is of the type described in the publications previously referred to. Loadcells 9, designed to measure the rolling load (F), are interposed either between each of the lower back-up roll chocks and the housings as shown in FIGS. 1 and 2 or between the pistons and the upper backup roll chocks with which they engage, as shown in FIG. 3. These loadcells supply an electrical signal proportional to F and the signal is modified in a circuit component 10 so as to be equal to F/ M where M is the elastic constant of the mill. Each assembly has its own positional control system including its transducer 8, comparing means 11 and a servo valve 12 which controls the flow of hydraulic fluid to and from the assembly. The transducers 8 indicate electrically the position of the piston of the assembly with respect to its cylinder and the output from the transducer is compared with a datum signal to produce a ditferent signal which is used to control the valve 12 to adjust the position of the piston until the difference signal is reduced to zero. The datum signal for the positional control system of the piston-and-cylinder assemblies is derived from the slider of a potentiometer 14, driven by a motor 15; the signal from the potentiometer is also used as the S0 or roll setting signal. Lastly, a signal representing the required thickness of the strip to be rolled is derived from a manually set potentiometer (not shown); this is the h signal of the Sims and Briggs paper. The three signals, S0, F/M and h, are combined as described in the paper in comparing means 16 to produce a gauge error or difference signal representing the departure of the thickness of the strip leaving the mill from the required value (h') and this error signal e is applied to the motor 15 driving the slider of the potentiometer providing the datum signal for the positional control systems.

In operation, when a gauge error appears, the motor 15 is driven to alter the setting of the datum signal potentiometer and thus to change the positions of the pistons of the piston-and-cylinder assemblies until the gauge error substantially disappears, when the thickness of the strip has been returned to the required value.

When it is required simply to control the mean thickness of the strip to the desired value, the signals from the two loadcells in the two housings are applied in common to the automatic gauge control system and the datum signal from the datum position potentiometer are applied in parallel to the positional control systems of both pistonand-cylinder assemblies. However, if the shape of the strip is also of importance, there is a separate control system for each housing supplied with the signal from the loadcell of that housing and controlling the positional datum of the piston-and-cylinder assembly of the same housing. In order to speed up the response time of the control system of such an arrangement, the positional control system is constituted by the gauge control circuit as shown in FIG. 4. The output signal from each transducer which indicates the position of the piston of that assembly indicates the roll gap setting S and is added to a signal proportional to F/M from the loadcell in a control circuit 20 and is compared with an input signal h which is proportional to the desired thickness of the material being rolled. The output signal from the control circuit 20 is a difference signal proportional to S0+F/Mh and is use used to control a hydraulic valve 21 which in turn controls the How of fluid to and from the assembly 7 whereby the position of the piston is adjusted until the difference signal is reduced substantially to zero.

FIG. illustrates a rolling mill having work rolls 1 and 2, and back-up rolls 3 and 4 journalled in the windows of a pair of housings, one of which is indicated by reference numeral 5. Each housing is provided with a nut 30 into which is threaded a screw 31. The two screws are each connected through mechanical gearing and transmissions to individual motors 32 for raising and lowering the screws. Hydraulic piston-and-cylinder assemblies 33 are interposed between the lower end of the screws and the upper surface of the adjacent back-up roll chocks and are arranged to act in series with the screws so that coarse adjustment of the roll gap is provided by the screws and fine adjustment is provided by the assemblies. A control circuit for controlling the mill to produce a rolled product of substantially uniform gauge is shown in FIG. 6. Each motor 32 has a position transducer 34 associated therewith to provide an electrical signal S which is proportional to the position of the mill screw driven by the motor. Each assembly has a transducer 35 which produces an electrical signal S0 proportional to the position of the piston of the assembly relative to its cylinder. A loadcell 37 interposed between the lower back-up roll chock and the housing produces an electrical signal which is proportional to the rolling load F. These signals are supplied to a computing circuit 38 where they are summed and then compared with a signal h supplied to the computing circuit which is proportional to the desired thickness of the material being rolled in the mill to produce a difference signal. The difference signal controls a hydraulic valve 39 which regulates the flow of hydraulic fluid under pressure to or from the assembly 33 to adjust the roll gap in order to reduce the difference signal from the computing circuit 38 substantially to Zero. If it is desired to control the shape of the material being rolled, the signal 5,, S0 and F from one housing of the mill are supplied to one computing circuit and the output signal from the circuit employed to control the assembly associated with that housing while a further computing circuit receiving signals from the other housing is employed to control the assembly associated with the other housing.

In accordance with the provisions of the patent statutes, we have explained the principle and operation of our invention and have illustrated and described what we consider to represent the best embodiment thereof.

We claim:

1. A rolling mill comprising hydraulic piston and cylinder assemblies, each having a cylinder and coacting piston and positioned to adjust the gap between the work rolls; a supply of liquid under pressure; means for controlling the passage of liquid from said supply to said cylinders; for each said assembly, a position transducer for giving an electrical transducer signal representing the instantaneous position of the piston relative to its cylinder; an automatic control system comprising means for detecting departure of the thickness of material being rolled by the mill from a required value and for generating a datum signal in accordance with that departure; means for comparing said transducer signals with said datum signal to produce a difference signal; and means controlled by said difference signal for controlling said controlling means to adjust the positions of said pistons relative to said cylinders to reduce said difference signal to zero.

2. A rolling mill as claimed in claim 1 in which said automatic control system includes means for producing an electrical rolling load signal proportional to the rolling load in the mill, means for generating a desired thickness signal proportional to the desired thickness of the material being rolled, means controlled by said transducer signals, said rolling load signal and said desired thickness signal for generating an error signal representing the variation of thickness from the desired thickness, and means controlled by said error signal for varying said datum signal of at least one of said assemblies, whereby the position of the piston of at least one of said assemblies is adjusted relative to the cylinder to reduce said error signal substantially to zero.

3. A rolling mill comprising hydraulic piston and cylinder assemblies, each having a cylinder and coacting piston and positioned to adjust the gap between the work rolls; a supply of liquid under pressure; means for controlling the passage of liquid from said supply to said cylinders; for each assembly, a position transducer for giving a transducer signal representing the instantaneous position of the piston relative to its cylinder; an altomatic control system including means for producing a rolling load signal proportional to the rolling load in the mill, means for generating a datum signal proportional to the required thickness of rolled material, means controlled by said transducer signals, said rolling load signal and said datum signal to produce an error signal representing the departure of the rolled thickness from the required value; and means controlled by said error signal for adjusting said controlling means of at least one of said assemblies in a direction to reduce said error signal.

4. A rolling mill as claimed in claim 3 comprising also screw means additionally for adjusting said roll gap, and means for deriving a signal representing the position of said screw means, said error signal producing means being controlled additionally by said screw position signal.

References Cited UNITED STATES PATENTS 2,119,390 5/1938 Iversen 72-245 3,003,374 10/1961 Smith 72245 3,128,630 4/1964 Briggs 73432 3,186,200 6/1965 Maxwell 72-8 3,355,918 12/1967 Wallace 7216 3,389,588 6/1968 Reinhardt et al. 72-8 3,178,919 4/1965 Varner -c 72-9 3,286,495 11/1966 Diolot 728 3,355,925 12/1967 Barnikel et a1 72244 MILTON S. MEHR, Primary Examiner U.S. Cl. X.R. 7219, 21, 245 

